1. Field of the Invention
The present invention relates to an organic light emitting display, and more particularly, the present invention relates to an organic light emitting display that easily prevents a material used to form source and drain electrodes from being diffused into an active layer and reduces contact resistance between the source and drain electrodes and a first electrode.
2. Description of the Related Art
In recent years, many displays have tended to be replaced by portable thin flat panel displays. An example of such a flat panel display is an electroluminescent display. Electroluminescent displays are self-emitting displays having a wide viewing angle, good contrast, and rapid response speed, and thus, have been spotlighted as next generation displays. In particular, organic light-emitting displays including a light-emitting layer formed of an organic material exhibit better brightness, driving voltage, and response speed characteristics than inorganic light-emitting displays, and can form multicolored images.
Active matrix organic light emitting displays include a Thin Film Transistor (TFT) connected to an organic light emitting device. A source electrode or a drain electrode of the TFT is electrically connected to a pixel electrode of the organic light emitting display. A voltage is also supplied to an opposite electrode facing the pixel electrode. As a result, an organic light emitting layer disposed between the pixel electrode and the opposite electrode emits visible light.
The source electrode or the drain electrode of the TFT contacts an active layer. Each of the source and drain electrodes includes a metal, such as aluminum (Al), for low resistance. The active layer includes silicon (Si). The metal, such as Al, used to form each of the source and drain electrodes may be diffused into the active layer. The diffusion becomes severe in a high temperature process, such as a thin film forming process, thereby short-circuiting the active layer or deteriorating channel characteristics.
The pixel electrode contacting the source and drain electrodes may include Indium Tin Oxide (ITO). Contact resistance between metals used to form the source and drain electrodes and ITO used to form the pixel electrode is higher than a resistance between the metals. In particular, when each of the source and drain electrodes is formed of a single metal, Al, an oxide is formed on a surface of each of the source and drain electrodes, thereby further increasing contact resistance between Al and ITO.